How-To Guide: Easily Convert Your Photo to Grayscale Using Luminance and LAB Mode

Easily Convert Your Photo to Grayscale Using Photoshop LAB Mode

Article by Jeanette Smith

There are several methods for creating a grayscale photo in Photoshop. One way is not necessarily better than another, it's simply a matter of personal preference and your comfort level with Photoshop. To name a few methods, you could use the RAW Converter, various adjustment layers such as Hue/Saturation, Channel Mixer or Black & White, or the method I've chosen for this tutorial — the LAB Color Mode.

This "additive" method, as opposed to an editing or corrective method, takes advantage of the Luminance Channel in the LAB Color Mode. I particularly like this method because

it is non-destructive to your original photo, which is always the best way to go when making any kind of adjustments or changes to your photographs;
it uses a Blending Mode that gracefully combines areas of overlying pixels, adding richer color effects;
and adds saturation, unlike many other methods.

In short, with this method, we are utilizing different color spaces, going from RGB to Lab Color to Grayscale, in order to capture the luminosity, or lightness, of an image. We inverse this to achieve the darkness of the image, then isolate that treatment on a new layer, and finish by blending it with the existing layer.

With this process, we can utilize the native light contained in the image, which is always a good idea for getting the most natural results, because it captures the subtle light-to-dark transitional tones that keep the photo looking alive and fresh, not altered and dull.

Let's Get Started

The first step is to change your color space to Lab (which stands for Lightness, or luminosity), plus A and B axis, which represent opposed color channels of red-green and yellow-blue. Image > Mode > Lab Color
In the channels panel, highlight the Lightness channel. Your image will appear as grayscale.
Now convert your image to grayscale mode. Image > Mode > Grayscale
Load the grayscale channel as a selection by holding the Command key and clicking once on the channel thumbnail. [Optional: you can change the color of this layer to get a tinted effect.]
Inverse the selection. Select > Inverse
Now convert the file back to the RGB color mode. With the selection still active, go back to the Layers panel and go to Layer > New > Layer via Copy (Command J). This will put the selection on a new layer with the contents of the original layer.
Apply the Multiply Blending Mode to this layer. Merge it with the original layer.

The most important result when processing your photos in Photoshop is that you are happy with the final image. There is no patently right or wrong way to achieve this; as with any part of photography, the end result should be an image you are proud of, and one that tells a beautiful story...how you got there is a matter of your own personal choice.

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